Currently, in place of a paper publication such as a book, a magazine, a newspaper, etc., an electronic book has attracted attention and has increasingly proliferated. An electronic book is an electronic medium that allows the content of each page to be displayed on a display screen of a display unit of an electronic-book display device, enabling a user to read the content of the electronic medium. An electronic-book display device includes terminal equipment exclusively designed for displaying electronic books, such as an electronic-book reader, and a mobile information device having multiple functions one of which is to display electronic books, such as a smart phone, a tablet computer, etc.
Patent Document No. 1 discloses an electronic display device as an example for use in an electronic book, in which there are a display screen and an outer frame disposed outside of the display screen, wherein the outer frame is locally occupied with a grip intended to be held by a user with a hand, and the grip is equipped with a touch sensor manipulated by the user with a finger of the hand. This electronic display device allows the user to interact with the electronic display device for commanding a page-up or page-down event using the user's one hand holding the electronic display device.
In this electronic display device, a control to be manipulated by the user for commanding page turns is located outside of the display screen. Many other electronic-book display devices, however, have a touch panel serving as the control, which is laid over the display screen in order to maximize the size of a display screen on which pages are displayed, within the limits of the overall size of each device. These other electronic-book display devices allow the user to perform a variety of inputs via finger touches of the touch screen for invoking reading or browsing.
Thus, many display devices are designed, for example, to allow a user to touch the finger to a touch panel laid over a display screen on which pages are displayed, to command page turns on the display screen. In addition, as disclosed in Patent Document No. 2, there is another type of image display device designed to turn pages in a manner that responds to motion of a user's finger in contact with and across a touch panel. This image display device disclosed in Patent Document No. 2 is further designed to allow the user to select the number of pages that are to be turned at a time on the display screen, by changing the number of ones of the user's fingers which touch the display screen altogether.